People tend to divide Robert A. Heinlein's career into three different eras, with the "juveniles," the "slick" science fiction stories, and the bigger, more opnionated novels. But over in Locus Magazine, Gary Westfahl has a theory that's sure to be controversial: Heinlein's career actually divides into a slew of serious novels, followed by a swerve into satire.

In particular, Westfahl points out how Have Space Suit - Will Travel is like a more tongue-in-cheek version of Rocket Ship Gallileo, Heinlein's first juvenile. And Starship Troopers and Podkayne of Mars similarly seem to be lampooning earlier books, Space Cadet and Between Planets. Westfahl even offers an explanation for why Heinlein might have changed gears around 1957 — for one thing, he'd completed his future history cycle, but for another, there was a very specific event that year:

As to why this sea change in Heinlein's career occurred in the year 1957, there is one obvious event to consider: the October, 1957 launch of Sputnik, humanity's first venture into outer space, which a man like Heinlein may have reacted to in two ways. First, there might be a sense of vindication: although Heinlein's stories and novels for adults had involved a variety of topics and themes, each and every one of his juveniles had focused on space travel, suggesting an intent to persuade Americans that, more than anything else, humanity's future depended upon vigorous expansion into space. Sputnik clearly indicated that Heinlein and other science fiction writers had succeeded in achieving this goal: humans were finally venturing into the cosmos, and everyone in the science fiction community had long been confident that, once space exploration had started, further progress to the Moon, Mars, and beyond was virtually inevitable. Thus, Heinlein might have thought, with its serious purpose accomplished, science fiction could now relax and be dryly humorous instead of earnestly didactic. A second reaction might be alarm, inasmuch as it was the communist Soviet Union, not the democratic United States, that had taken the lead in the space race, creating the strong possibility that they would soon dominate space, and thus dominate the Earth as well (precisely the argument Heinlein had made in Destination Moon). As his nonfictional response to this ominous threat, Heinlein had briefly attempted to launch a political movement with his 1958 advertisement-essay "Who Are the Heirs of Patrick Henry?," shrilly arguing that a planned nuclear test ban treaty would amount to surrendering America to the insidious communists. Arguably as his fictional response, then, Heinlein might have turned to the natural tool of the distressed writer, satire; thus, among other things, Starship Troopers can be read as Heinlein's take on the Cold War, with loathsome, insect-like aliens standing in for the Russians. Later, when Heinlein was reassured by America's space initiatives and realized that a test ban treaty was not going to mean the end of the world, the new satirical approach he had adopted would gradually lose its hard edge and become more playful.